This invention employs a gaseous wave refrigeration method and has its application in a low temperature separation process by energy recovery of pressurized gases. This invention is designed to generate cooling and heating effects by the use of the resonant periodic flow phenomenon and wave interactions in the gaseous wave refrigeration device of the system.
In traditional chemical and petroleum industries, numerous gaseous refrigeration processes and systems are applied in the operations of condensation, separation, liquefaction, and refining. Generally, cooling capacities in those systems are provided by gaseous expansion equipment, such as turbines and piston expanders operated under pressurized gases. Although gaseous expansion machines used in conventional energy convening systems have high efficiency, they require steady working conditions and a proper range of pressure drop ratio and flow rate. Such requirements of working condition, associated with their complicated mobile mechanical structures, result in high initial investment and considerable maintenance cost. Therefore, in many practical cases where gases are discharged with a high pressure drop ratio and a small flow rate, and where working conditions are fluctuating with losses of pressure energy, these traditional refrigeration systems and devices work with lower efficiency or ineffectiveness. Generally, to achieve the pressure reduction in the special technical process, a simple throttling valve is employed instead of traditional refrigeration machines but this is achieved at the cost of pressure energy loss for the capacity of system to work under extreme working conditions and its structural simplicity.
On the other hand, during the last few decades, due to the development of new technological processes, the shortage of energy resources, and worldwide protection of the environment, there has been an increasing interest in developing new refrigeration methods and systems that work under some special conditions, including high ratio of pressure drop or variable operating condition in order to replace inefficient traditional equipment and possess merits of simple structure, no leakage of the harmful materials, low initial investment, and low maintenance cost. Considerable improvements have been made in this field for consideration of high effective operation or recovering energy. One of the successful methods is to create cooling effect by means of gaseous wave interaction and interchange in periodic unsteady flows as is employed by U.S. Pat. Nos. 3,541,801, 3,653,225, 3,828,574, 4,625,517, and 4,722,201. In U.S. Pat. No. 3,541,801, the periodic gaseous motion in the receiving tubes is created by means of a bistable sonic oscillator instead of the reciprocating motion of the piston for a pulsating flow production. However, because such an operation is based on a simple combination of receiving tubes with fluidic bistable control elements, the apparatus of U.S. Pat. No. 3,541,801 works only with two resonant tubes and on very limited scale of mass flow rate and geometrical size. In the system of U.S. Pat. No. 3,828,574, a similar working process is accomplished by a mobile mechanical device called a rotary distributor. Such a device relies on a complex sealing structure with some moving parts which lead to a limited lives, a possibility of leakage of working fluid, a necessary requirement of special lubrication of parts, and high maintenance cost. Patents, as was mentioned above, (U.S. Pat. Nos. 3,541,801, 3,828,574) both use the phenomenon of pulsating flow to produce cooling and heating effects. In other systems such as U.S. Pat. Nos. 4,625,517 and 4,722,201, periodic thermal advection and the thermoacoustic oscillation are induced by means of a stack of thin, well-spaced stainless-steel plates and a set of spaced apart copper strips which convert heat energy absorbed from the high temperature heat source into acoustic power for pumping heat from one low temperature source at the system's one end to a high temperature sink at the other end of the system. Both systems described in U.S. Pat. Nos 4,625,517 and 4,722,201 provide a similar method which utilizes directly heat energy absorbed from high temperature environment to create acoustic resonant phenomenon, and extract heat from a cold space for supplying a cooling effect.
In summary, the prior patents have some serious limitations in terms of their efficiency and scope of applications. First, although there are several forms of gaseous refrigeration system which used a pulsating flow for refrigeration as reported in prior an patents, it is difficult to find an effective device which has enough cooling capacity, is free of complex structure and moving parts, and is suitable for the scale of flow in industry practice. Second, it is also very difficult for the aforementioned types of gaseous cooling devices to work effectively (or to be more specific, they will be limited in capacity, and won't have the required stable operation) on some particular operating condition, especially in the case of the high pressure drop ratio with small flow rate and unsteady operating conditions. Therefore, these and other difficulties experienced with prior art system and the needs of engineering applications have been motivated in a novel manner of the present invention.
Compared to traditional refrigeration equipment and the types of gaseous wave refrigeration machines aforementioned, the present invention, for its primary object, introduces a method which works by the a new mechanism of pulsating flow production which provides a resonant gaseous wave cooling processes and overcomes the limitations and weak points of conventional machines. A steady effective operation in applicants apparatus is based on such special operating mechanism of a pulsating flow production and designed structure for such an aim to be used effectively in separation and liquefaction for pressure energy recovery and reuse from pressurized gases in industrial settings. Such a method is especially suited for some special technological processes in industries where the high pressure energy is wasted. Therefore, the gases wave refrigeration method accompanied with energy recovery system of the present invention provide an effective operation for the following processes: a), where exhausting natural gases rush out with crude oil extraction under the conditions of a high pressure drop ratio, low and unsteady mass flow rates during the initial stage of oil extraction, so that it is difficult for the discharged gases to be collected and processed in such a flow state; b), where pressurized waste gases, which may contain some pressure energy as well as some harmful or pollutant components but that could be worth recovering as raw chemical materials in some special technological processes of chemical, petroleum and oil refined industries, are discharged and burnt; where the pressure reduction of a working fluid for the requirement of special technical processes with a steady or variable flow condition is completed by means of a throttle valve in which the pressure energy in the working fluid is dissipated by the throttling effect; c), where some special gaseous refrigeration processes with direct recirculation of refrigerant are required.
In short, present invention aims at meeting several important objects. The first is to provide a gases wave refrigeration method and apparatus with an energy recovery system for applying in the case where traditional expansion machines can not be used or are used with the price of low efficiency.
The second is the provision of a gases wave refrigeration method and apparatus with an energy recovery system for recovering the high pressure energy from the industrial discharge of gases.
The third is the provision of a gases wave refrigeration method with an energy recovery system for a wellhead processing system for recovering the valuable hydrocarbon compositions from discharged associated natural gases during the initial stage of extraction in either off-shore or isolated land oilwell extraction, wherein generally it is so hard to gather and process those gases because of the high pressure difference, low flow ratio or fluctuating operating condition that those natural gases have to be burned out to protect the environment and to prevent the explosion.
The fourth is to provide a gases wave refrigeration method with an energy recovery system to collect the harmful or polluting compositions from the pressurized waste gases in chemical, petroleum, and oil refining industries.
The fifth is to provide a gases wave refrigeration method for the special gaseous refrigeration processes where the refrigerant is circulated directly without the need of recycle by passing a heat exchanger.
The sixth is the provision of a gases wave refrigeration method with a device to replace throttle valves so that the system may work normally under the working conditions of high pressure drop ratio with unsteady mass flow rate.
The last is to provide a gases wave refrigeration method and apparatus with an energy recovery system which is able to operate under the extreme high pressure drop by means of a multi-stage operation without using any moving parts, such as throttle valves in series.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.